Find the four roots of
\[2x^4 + x^3 - 6x^2 + x + 2 = 0.\]Enter the four roots (counting multiplicity), separated by commas.
Explanation: Dividing the equation by $x^2,$ we get
\[2x^2 + x - 6 + \frac{1}{x} + \frac{2}{x^2} = 0.\]Let $y = x + \frac{1}{x}.$  Then
\[y^2 = x^2 + 2 + \frac{1}{x^2},\]so $x^2 + \frac{1}{x^2} = y^2 - 2.$  Thus, we can re-write the equation above as
\[2(y^2 - 2) + y - 6 = 0.\]This simplifies to $2y^2 + y - 10 = 0.$  The roots are $y = 2$ and $y = -\frac{5}{2}.$

The roots of
\[x + \frac{1}{x} = 2\]are 1 and 1.  The roots of
\[x + \frac{1}{x} = -\frac{5}{2}\]are $-2$ and $-\frac{1}{2}.$

Thus, the roots of $2x^4 + x^3 - 6x^2 + x + 2 = 0$ are $\boxed{1, 1, -2, -\frac{1}{2}}.$